PM7344 S/UNI-MPH
DATA SHEET
PMC-950449
ISSUE 6
MULTI-PHY USER NETWORK INTERFACE
Figure 16
- HCS Verification State Diagram
ATM DELINEATION
SYNC STATE
ALPHA
consecutive
incorrect HCS's
(To HUNT state)
HCS Multi-bit Error Detected
(Cell discarded)
Cell
Accepted
Correction
HCS Single-bit
Error Detected
Cell
(Error corrected
& cell accepted)
Discarded
Detection
No HCS Errors Detected in M
Consecutive Cells
DELTA
(M'th Cell Accepted)
consecutive
correct HCS's
(From PRESYNC
state)
The RXCP accumulates the number of received assigned cells, received
unassigned/idle cells, cells containing a correctable HCS error and cells
containing an uncorrectable HCS error, in saturating counters.
9.17 Receive ATM 4 Cell FIFO (RXFF)
The Receive FIFO (RXFF) provides FIFO management and the S/UNI-MPH
receive cell interface. The receive FIFO can hold four cells (note that the
effective working FIFO depth is actually three cells because if four complete cells
are being held in the FIFO, the next information bit transmitted to the RXCP,
even if it is part of a null cell, will cause a FIFO overflow). The FIFO provides the
cell rate decoupling function between the transmission system physical layer and
the ATM layer.
In general, the management functions include filling the receive FIFO, indicating
when the receive FIFO contains cells, maintaining the receive FIFO read and
write pointers, and detecting FIFO overrun and underrun conditions.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
58
PMC [ PMC-SIERRA, INC ]
